import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.text.DecimalFormat;

public class 数的三次方根 {
    public static void main(String[] args) throws IOException {
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        PrintStream out = new PrintStream(System.out);
        double n = Double.parseDouble(in.readLine());
       DecimalFormat df = new DecimalFormat("0.000000");
        /* System.out.println(df.format(Math.cbrt(n)));*/
        double l = -10000;
        double r = 10000;
        while(r-l>1e-8) {
            double m = (l+r)/2;
            if(m*m*m>=n) r=m;
            else l=m;
        }
        System.out.println(df.format(l));

    }
}
